Method of producing ethers and esters of carbohydrates



Patented Jan. 11, 1949 METHOD OF PRODUCING ETHERS ESTERS OF CARBOHYDRATES J an Lolkema, Hoogezand, Netherlands; vested in the Attorney General of the United States N Drawing. Application February 25, 1941, Se-

rial No. 380,562. In the Netherlands January 23, 1940 Section 3, Public Law 690, August 8, 1946 Patent expires January 23, 1960 asse DEC 18' 1951 9 Claims. (01. 260209) 1 2 The invention relates to a method of producethers and esters from other polysaccharides ing ethers, esters and mixedether-esters of carwhich likewise will produce viscous, sticky solubohydrates, more particularly of starch in a dry tions both in cold and hot water. form which are soluble in cold or in hot water The invention will now be described with reor in both. 5 gard to the production of starch ethers.

There are already known several methods of According to an embodiment of the invention producing alkyl ethers of starch. In general they the starch is first mixed with a small proportion are obtained by treating an aqueous suspension or of water (i. e. the proportion usual for the propaste of the starch with the alkylating agent, duction of cold swelling starch) and with the e. g. an alkyl sulphate, in the presence of a subchemicals required for etherification and, prefstance having an alkaline reaction. According erably after the etherification process has proto these methods the ethers are generally obceeded to a smaller or larger extent, subjected to tained in the form of colloidal solutions or pastes the heating process described above. which can be used as adhesives. The production This process may be carriedout by stirring the of the solid ethers in a dry condition from these 1!; Starch e. g. with from /2-2 parts by weight of reaction products is known likewise; for this purwater and subsequently adding the quantity of the pose, however, comparatively laborious and exalkaline substance required for the reaction. As pensive treatments were necessary, such as e. g. such e. g. alkali hydrates, salts having an alkaiprecipitation with alcohol, separation by dialysis line reaction, ammonia or organic bases may be or separation by adding inorganic salts with subused. The addition of the said alkaline subsequent filtering, washing and drying. The stances is necessary in most casesfor effecting the products thus obtained were readily soluble in reaction with the etherifying agent. cold water, but only slightly soluble in hot water. The etherifying agent e. g. a dialkyl sulphate is Up to the present the said starch ethers have been now added to the said mixture while stirring. In but little used for technical purposes, which is order to accelerate the reaction, the reaction mixpartly due to the laborious methods of producture may be heated, but since the reaction is exoing the same. thermic, this generally will not be necessary and in The production of ethers of other carbohysome cases cooling is even advisable, in order to drates and of esters of carbohydrates is also retard the reaction. known. Up to the present, however, they have The mixture is now suddenly heated during a also proved to be of small importance in actual short time to a high temperature and pressed or practice. spread out to form thin layers which are-simul- The present invention relates to a method taneously dried. This operation which is well which renders it possible to produce in a very known from the manufacturing processes of cold simple and economical manner from starch and swelling starch of which it forms an essential other carbohydrates which may be made into a part, is preferably carried out by applying the solution or paste by stirring them with a small mixture to rotating cylinders heated to a temperproportion of water, ethers, esters and mixed ature of 100 C. or above, which are positioned so ether-esters in the form of dry flakes or powders that the mass is pressedinto a thin layer. The which are readily soluble in cold and/or hot 40 starch will thereby be gelatinized in so far as water. This method consists in that a mixture of gelatinizing has not yet been efiected by the althe carbohydrate with a limited quantity of Water kali during the pre-treatment, and simultaneeither after the etherification or esterification or ously dried, so that the material leaving the cylin any desired stage of the said processes, is sudinders will consist of thin sheets or chips which denly heated fora short time to a, high temperamay be ground, if desired. ture and pressed out or spread out to form their Before the mass is submitted to thistreatment, layers which are simultaneously dried. If gelaa more or less advanced etherification of the tinizable carbohydrates are used as a starting starch has already taken place; preferably operamaterial the reaction mixture is preferably heated tions are carried out in such a way that the reacto a temperature above the gelatinizing tempertion will be accomplished for three quarters or ature. more before the material is heated and dried on The invention ischiefiy important for the prothe cylinder. duction of valuable products from starch or During this latter treatment the etherification starch containing materials and starch derivaprocess will proceed, particularly because of the tives, but it may also serve for the production of fact that owing to the evaporation of the water the concentration of the unreacted part of each component will increase very quickly, whereby the reaction will be considerably.accelerated. It has accordingly been found that the etherification process'is completed Within a short time and that in a few minutes a dry product of the desired degree of etherification is obtained. The method according to the invention therefore renders it possible to utilize the etherifying agent as completely as possible in a very simple .andinexpensive way.

Instead of immediately adding the entire quantity of alkaline substance to the starch-water mixture, it is also possible to add the same entirely or partly together with the etherifying agent. It is also possible first to mix theistarch with the water and the etherifying agent and subsequently to add the required quantity of the alkaline substance.

The etherifying agent may be diluted, if desired, with a solvent; this solventjhowever, must not have too'higha'boiling point, as itwillhave to evaporate again during thetreatment on the cylinders. j

The alkyl groups furthermore may have straight or branched chains which may be interrupted by oxygen, nitrogen or sulphur.

The starch may also be etherified with different groups. In that case the starchis reacted with two or more etherifying agents which may be added either'simultaneously or successively and "in any desired sequence, eitherin immediate succession or at'given'intervals. Examplespf such mixedstarch ethers'are the methyl ethyl ether and the methyl-hydroxy.2 ethyl ether.

" When usingtheterm ethers of carbohydrates in the specification and claims I only mean those compounds in which "one carbon atom does'not contain more than one hydroxy alkylgroupand it therefore does not include the compounds known under the name "of acetales which are obtained by reacting aldehydes of ketones 'with hydroxy compounds; e g. the condensation products of carbohydrates with formaldehyde.

The invention has been describedabove for the productionof starch ethers, butthe esters may also be-prepared in a similarmanner; e; g. bymixing'the starch with a small proportion oiwater and an alkaline substance, subsequentlyadding an acid chlorideand'after the reaction hasproceeded for a considerable part,heatingthe'mixture'oncylinders in themanner described above.

The esters used accordingto 'the-inventionare derived from polybasic inorganic'or from monoor from polybasic organic acids, e. g. aliphatic or aromatic acids, which may also contain'one or more of the above mentioned'substituents. The term esterifying agents when usedin the specification and claims is not meant to include carbon disulphida'which, although it is not. an esterifying agent in the usual sense,-is capable of forming xanthates when'mixed with carbohydrates in the presence of alkali.

Furthermore it is also possible to produce mixed etheresters by treating the starch both with etherifying and esterifying agents. If the addition of the esterifying agent occurs simultaneously with or after the addition of the etherifying-agent; the esterifying agent'mayreact with free hydroxyl groups of 'the'starch aswell as with certain groups, e. g. hydroxyl' or amino groups present in the etherifyingngenteither be'fore or afteresterification, or with both.

The best known and c'hieflypsed etherifying agentsarethe' esters "of the corresponding alcohols e. g. with acids such as sulphuric acid. In the etherifying process this acid will be partly or entirely liberated and for this reason it is generally-,necessary to add alkaline substances which combine with the acid. It is, however, also possible to employ etherifying agents which do not produce acids, such as the epoxy alkanes. Never- .theless it willbeladvantageous in this case also toadd alkaline substances as they will act as catalysts. After thereaction has been completed, the alkaline substance may be partly or completely neutralized.

The-alkyl groups which may be combined with the starch by .theetherifying process may be of a varying character and they may contain various substituents, e. g. one or more hydroxyl groups, mercapto groups, rhodanide groups, halogen atoms, amino or substituted amino groups, cai-boxyl groups or arylcarboxyl groups or alkali salts respectively, alkaline earth salts or other salts or 'functional' derivatives thereof, such as amides and substituted amides, sulphonic acid groups or aryl sulphonic acid groups, or salts or functional derivatives thereof and the like.

Similar derivatives as described above in connection with starch may also be'produced from starch products as soluble 'starch,dextrine and the like, and from other carbohydrates, such as inuline, sugars, different kinds'of gums, such as gum arabic, and the like, in so far as they can be made into a solution or paste by stirring the same with a small proportion of watenand the products thus obtained are likewise soluble in cold and/or hot water. "By a small proportion of water I mean the proportion generally used in the manufacture of cold swelling'starch. Of course mixtures of different carbohydrates may also be used'as starting materials.

The methods of production described above are extremely simple, practicaland far less laborious than the methods used up to the'presout, which renders the "final'products less expensive.

When comparedwith the usual starch products used for technical'purposes e. g. the well known soluble starches, cold swelling starches, dextrines and the like, the starch ethers and esters according to the invention have different properties, which :gives them special advantages for various purposes. Depending on the nature and/or the quantity of the etherifying or the esterifyin agent usedper .unit ofglucose, one obtains products which dissolvedin water'toa colloidal solution will show a. great variationin regard to viscosity. The said viscous colloidal solutions are characterized .by agum-like character and a great and.lastingtransparency; they do not show. retrogradation phenomena and in .many cases will possess-a better solubility and a strongadhesive power.

They furthermore .have the advantage that they are not substantially attacked by .microorganisms, so that practically no preservatives need be added to .the adhesives produced-from the said ethersand esters. .Moreover the starch products thus produced willipractically form .no lumps when dissolved in cold .water, a drawback which asisknowmis generally-inherent to cold swelling starch products.

I claim:

.1. The process of manufacturing adhesive alkyl ethers of a gelatimzable carbohydrate soluble in water to Iiorm a-paste which comprises .mixing the carbohydrate With analkaline. solution and anetherifying agent, spreading the mixf ture to form a thin layer and quickly heating the layer to a gelatinizing temperature while evaporating the solution to accelerate the etherification.

2. The process of manufacturing adhesive alkyl ethers of starch soluble in Water to form a paste which comprises mixing the starch with an alkaline solution and an etherifying agent, spreading the mixture to form a thin layer and quickly heating the layer to a gelatinizing temperature while evaporating the solution to accelerate the etherification.

3. The process of manufacturing adhesive alkyl ethers of starch soluble in water to form a paste which comprises mixin the starch with an alkaline solution and an etherifying agent, spreading the mixture to form a thin layer and quickly heating the layer to approximately 100 C. until dry.

4. The process of manufacturing adhesive alkyl ethers of starch soluble in water to form a paste which comprises mixing the starch with an alkali hydrate and an etherifying agent, spreading the mixture to form a thin layer and quickly heating the layer to approximately 100 C. until dry.

5. The process of manufacturing an adhesive ether of starch soluble in water to form a paste which comprises mixing the starch with an alkaline solution and diethyl sulphate, spreading the mixture to form a thin layer and quickly heating the layer to approximately 100 C. until dry.

6. The process of manufacturing an adhesive ether of starch soluble in water to form a paste which comprises mixing the starch with an alkali hydrate and diethyl sulphate, spreading the mixture to form a thin layer and quickly heating the layer to approximately 100 C. until dry.

7.. The process of manufacturing an adhesive ether of starch soluble in water to form a paste which comprises mixing the starch with an alkaline solution and an etherifying agent and quickly pressing a thin layer of the mixture between surfaces heated to C.

8. The process of manufacturing an adhesive ether of starch soluble in water to form a paste which comprises mixing the starch with an alka line solution and an etherifying agent and quickly pressing a thin layer of the mixture between two rotating cylinders heated to 100 C.

9. The process of manufacturing an adhesive ether of starch soluble in water to form a paste which comprises mixing the starch with an alkaline solution and an etheri-fying agent spreading the mixture to form a thin layer and completing the etherification by heating thei layer to 100 C. until dry.

JAN LOLKEMA.

REFERENCES CITED The following references are of recordin the file of this patent:

American Dyestuff Reporter, June 19, 1933; p. 379, by Hall-Huntress. Problems in Organic Chemistry, page 71, McGraw-Hill (1938). 

